Examination of Witnesses (Questions 135
- 139)
WEDNESDAY 7 NOVEMBER 2001
PROFESSOR DAVID
KING, PROFESSOR
MARK WOOLHOUSE
AND DR
BRYAN GRENFELL
Chairman
135. Professor King, and Dr Grenfell and Professor
Woolhouse. Professor King, you are a sort of deus ex machina
of the Government, are you not, you sort of keep popping up from
time to time when there appears to be either something going wrong
or a crisis or a corrective to be applied, so we thought it was
about time you popped up again, so that is why we invited you.
We want to talk obviously about foot and mouth disease, though
there is the issue of BSE in sheep, the rather recent issue. You
have given us some charts. Jim Scudamore appeared before us last
week, and quite a large number of the pages in this were ones
he circulated and talked to last week, so I am anxious that we
should not go over the same ground twice, but if there are some
preliminary things you would like to say perhaps you would like
to do so? Could I say that this room is a sort of cavernous place
in which the acoustics are not easy for anybody, so we all try
to shout a little bit, and I am sorry about that but I did not
design it.
(Professor King) The FMD story document that I have
circulated I think will be materially different from the one that
Jim Scudamore would have circulated, for the simple reason that
this one dwells on the scientific input that my group had throughout
the FMD outbreak, and has to the present time. And, of course,
what it stresses is the importance of the scientific modelling
that was done to project forward from any point during the outbreak
as to what the outcome would be given various control scenarios.
So I think that would be the difference in emphasis.
136. That is helpful, and you will no doubt
refer to it from time to time during your remarks, but you do
not particularly want to sort of make a presentation based on
it?
(Professor King) The expectation was not to make a
presentation but rather to respond to questions.
137. That is a happy coincidence between your
view and my view. Could we start by just looking at where we are
on sheep, brains of, and all that. You were asked if you could
find out what had gone wrong and where we are going on this issue.
You will not need us to say that it is a bit of a sword of Damocles
hanging over the industry, lots of rumours and belief that if
BSE were seen to be present in sheep brains, screened by scrapie,
we would be into the universal slaughter of the flock, though
the Minister put that one to rest yesterday, I think. But it would
be helpful to know, are you yet able to find out what actually
went wrong in the famous experiment, and, I think, more importantly,
where are we heading in the experiment on the possible existence
of BSE in the modern day sheep flock?
(Professor King) Can I make first two preliminary
statements, and the first one would be to underline what the Food
Standards Agency is currently saying, though I certainly believe
that they are saying this with good reason, and that is that there
is no reason to deter people from eating lamb, British lamb. The
second point to make is that the test that is under scrutiny at
the moment was a test on sheep brain from a pool that was collected
over the period 1990-92 and is therefore not particularly relevant
to sheep in the field today. And so, whatever the outcome of that
test, meat and bonemeal was terminated in 1996 as feedstock, finally,
and so the possibility of BSE in sheep today is a question that
hangs over, whatever the results of that test. Your specific question
about how that came to be, that a test lasting such a long period
of time and costing quite a lot of money should apparently have
been done of a brain pool that was cattle brain rather than sheep
brain. There is an audit, as I am sure you are aware, currently
being conducted, it was requested by DEFRA, it is being done by
an independent firm of consultants; we had anticipated the results
of that audit round about the beginning of this week, and I believe
it has been delayed, so I have not yet seen the result. And there
is a second audit that will take longer, that is being conducted
by UKAS, and I expect that that will go into things in much more
detail. Until either of those audits is out, particularly the
first, I would not like to comment on whether or not the samples
were incorrectly drawn, as some would say, or whether, in fact,
the brain pool that was being examined was, in fact, cattle brain.
138. As we are going to get the results of those
audits, I do not think there is much profit in trying to pursue
that one now, especially as we have the Secretary of State in
front of us at this time next week, so that if we have some results
we will no doubt want to come back to that. Can you just look
forward though at the same issue, because, as you said, quite
rightly, what really matters is what is the state of the current
flock; we know that the Department wishes to accelerate the programme
of developing a scrapie-resistant national flock, and part of
that is included in the Bill which we will debate on Monday. But
where are we on the development of more effective, rapid tests
on live animals, to be able to distinguish between scrapie and
BSE, because that is at the heart of the present debate, is it
not?
(Professor King) The reason for the long period in
the tests at the Institute of Animal Health in Edinburgh was because
they were using the mice assay, which I think everyone regards
as the gold standard for distinguishing BSE prion from scrapie
prion. And what we are now investigating and pursuing with vigour
is the molecular tests, the tests based on biochemical analysis,
which can be conducted in 24 to 48 hours on a given animal. The
western blot technique has already been used with quite a number
of tests on scrapie sheep at the VLA, I believe the number is
in the region of 480, but this is a moving target; as we speak,
further experiments are being conducted. And, using this technique,
so far, all of the sheep with scrapie symptoms have shown scrapie
prion and not BSE prion. And this is actually a significant result,
because the BSE in sheep, when infected in the laboratory, the
sheep show the symptoms of scrapie; so if we are going to find
BSE in sheep it is most likely to appear in those sheep which
are showing scrapie symptoms.
139. They key is, when do you have sufficient
results, by whatever test, to be able to declare that, according
to any reasonable analysis, the flock is BSE-free? Jim Scudamore
told us, on several occasions, that as far as foot and mouth disease
we had not merely to be disease-free but we had to be virus-free
before we could declare ourselves to have got shot of the disease,
and clearly the samples you have to take to make that credible
are considerable. What do we need to demonstrate for you to be
able to sit there, absolutely confidently, and say, "I can
now say, with absolute certainty, insofar as one can in anything
in this business, that there is no BSE in our national sheep flock"?
(Professor King) I am going to reply with a statistical
answer. The normal position of uncertainty that we are prepared
to live with is a 95 per cent confidence limit, and, I have mentioned
a number of about 480 sheep being tested; if we randomly tested
300 sheep in the sheep population and found no BSE, we would have
a 95 per cent confidence that the incidence is less than 1 per
cent, but, of course, 1 per cent of 40 million sheep is a large
number. So what we need to do is bring that down to 0.001 per
cent before we would bring it down to a number small enough that
we would be assured that we really did not have BSE in the sheep
population. But you will understand that we will never be able
to do it for a sufficient number of sheep to have 100 per cent
certainty, unless we tested every sheep going into the food chain.
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